Batch system for producing chemical compounds and / or gases from pyrolyzed plastic waste feedstock

Abstract

Multiple pyrolysis batch reactors operated on a sequential time basis to convert plastic waste, along with solid inert residues, into chemical compounds and / or gas products. This operation ensures a steady, uninterrupted high production of products with little downtime. Undesirable by-products such as pollutants and vapors are removed in stages before recovering the desired pyrolysis products.

Description

[Technical field]

[0001] The present invention relates generally to the production of chemical compounds and / or gases from multiple batch reactors that independently pyrolyze plastic waste in a time-sequential manner. [Background technology]

[0002] Proper and environmentally-friendly disposal of waste, including plastic waste, is a problem throughout the world, including the United States. The various solutions proposed have generally proven inadequate, ranging from simply burying the waste in landfills to attempts to chemically modify plastic waste to produce recycled chemical compounds. Chemically converting plastics is preferred over landfilling, as it conserves the fossil resources used in the production of plastics. However, waste plastic recycling and chemical conversion solutions generally suffer from contaminants such as mixed waste plastics, food waste, chlorides and dyes. Thus, the overall recycling rate of plastics is very low, and recycled resins struggle to compete economically with virgin plastics. Pyrolysis is more tolerant of mixed waste and contaminants, and produces hydrocarbons suitable for processing back into fuels, lubricants, waxes, and even virgin-quality polymers. Summary of the Invention

[0003] The present invention overcomes these problems by using multiple batch reactors with limited processing time to chemically reform plastic waste to produce chemically reformed compounds such as various pyrolysis oils and gases. Examples of such compounds include diesel fuel, gasoline, heating oil, natural gas, kerosene, lubricating oils, waxes, and various gas products such as, for example, methane, ethane, propane, butane, pentane, alkanes of alkenes, and isomers thereof, or any combination thereof. Various C 1 ~C 5Since alkanes are generally gases at room temperature, they are heated by the heater H of the pyrolysis system shown in Figure 2. 1 ~H 5 etc.

[0004] The present invention generally relates to multiple batch reactors operated in a sequential time manner with respect to their loading, production of the various chemical compounds and gases mentioned above, and their subsequent discharge from the batch reactors. Such sequential production from multiple batch reactors has been found to be an efficient and practical method of producing high yields of the various oils and gases mentioned above with reduced contaminant levels.

[0005] In general, a method for producing and recovering chemical compounds and / or gas products from a plastic waste feedstock includes providing a plurality of separate pyrolysis batch reactors, at least one of said pyrolysis reactors independently capable of converting said plastic waste to said chemical compounds and / or gas products, and a solid inert residue (SIR). The method includes independently loading said plastic waste feedstock into at least two of said pyrolysis reactors in a time-sequential manner; independently pyrolyzing said plastic waste feedstock in at least one of said separate batch reactors in a time-sequential manner; and independently producing and discharging said chemical compounds and / or gas products, and said solid inert residue (SIR) from said at least one of said separate pyrolysis reactors in a time-sequential manner. [Brief description of the drawings]

[0006] These and other features of the present invention will become apparent to those skilled in the art to which this disclosure pertains from a reading of the following description in conjunction with the accompanying drawings.

[0007] [Figure 1]FIG. 1 is a schematic graph of a multiple batch reactor that sequentially converts a load of pyrolyzed plastic waste into suitable compounds and / or gases and discharges the same in accordance with the present invention.

[0008] [Diagram 2] FIG. 2 is a perspective view of a plastic waste pyrolysis reactor according to the present invention.

[0009] [Diagram 3] FIG. 3 is a graph showing the loading time, pyrolysis time and discharge time for six batch reactors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A process and apparatus for high production of chemicals and gases derived from the systematic pyrolysis of plastic waste feedstock is disclosed, which is an environmentally friendly system and prevents large amounts of said waste from being dumped in landfills, oceans, etc. The present invention does not relate to continuous input of feedstock to a pyrolysis reactor, such as 24 / 7 operation, but rather to multiple individual pyrolysis reactors that are sequentially loaded or fed with a fixed or limited amount of plastic waste feedstock within a limited loading time. The feedstock is reacted for a limited time, usually a few hours, typically with two or more time stages to allow preferential separation and recovery of undesirable components from the final product, generally resulting in complete conversion of most and preferably all of the feedstock to chemical compounds and / or gases. Once the pyrolysis reaction cycle, i.e., reaction step, is completed, the remaining chemical compounds and gases are vented, i.e., produced and released from the reactor. An important aspect of the venting cycle or step is the complete removal of any remaining SIR (solid inert residue), which tends to remain or remain in the pyrolysis reactor and must be removed by airlock valves, pistons, augers, etc. The batch reactor is then ready to repeat the above three cycles of loading the pyrolysis reactor, pyrolysis of the feed therein, and finally venting or removing the remaining gases, liquids, and importantly, the remaining SIR materials. In accordance with the present invention, a series of reactors are utilized to operate on a sequential time basis, avoiding the costly and time-consuming slowdowns and / or shutdowns that can occur in continuous (24 / 7) pyrolysis operations, i.e., when the feed is continuously fed to the pyrolysis reactor for at least several days. Also, such continuous reactors are subject to various disturbances or failures of the pyrolysis reactor mechanism, such as improper heating, overfeeding or underfeeding of the plastic waste feed, inappropriate compounds contained in the plastic waste feed, residue build-up, coking, etc.

[0011] Referring to FIG. 1, a plurality of batch reactors are shown, with the operation of any given set of reactors generally arranged in a chronological order, for example, with respect to the reactor's production cycle of loading, pyrolysis reaction, and discharge. In other words, the plurality of reactors are operated on a timed sequential time basis relative to one another to achieve systematic processing of the plastic waste feedstock. The number of such pyrolysis reactors may vary widely, such as at least about 2 to about 12, often about 4 to about 9, preferably about 5 to about 7, etc. Although it should be understood that many variations can be used, the loading operation of the batch reactor system of the present invention (e.g., FIG. 2) is generally as follows. Plastic waste or plastic feedstock 2 contained in a plastic waste container 1 is independently conveyed or fed in a sequential time manner to the various individual reactors I-VI of FIG. 1 via one or more feed lines 21 using standard feeding mechanisms such as conveyors, augers, extruders, airlock valves, and the like. The feedstock is initially preferably fed only to reactor I, then only to reactor II, and thereafter only to reactor III. In the embodiment shown in Figure 1, six reactors are used, with the last reactor, i.e., reactor VI, being loaded last. More specifically, feedstock 2 is fed into the reactor opening 3 shown in Figure 2. The charging time between feedstock additions can range from about 15 to about 180 minutes, desirably from about 60 to about 150 minutes, and preferably from about 110 to about 130 minutes, i.e., about 2 hours.

[0012] Once the entire finite amount of raw material is loaded into the reactor, the heater H 1 and H 2typically begins a reaction or pyrolysis step lasting from about 30 to about 300 minutes, preferably from about 60 to about 180 minutes, and most preferably from 90 to 120 minutes. Numerous pyrolysis methods can use such steps or cycles in the temperature range of about 500°F (260°C) to about 1500°F (816°C), preferably from about 700°F (371°C) to about 1300°F (704°C), and preferably from about 800°F (427°C) to about 1100°F (593°C). During the pyrolysis reaction, the feedstock 2 is gradually moved into or through the reaction vessel I, II, III, etc. by conventional transport devices such as helical screws, conveyors, assembly lines, etc., or by mixing devices. In the methods as described herein below, the various compounds of the feedstock 2 are pyrolyzed in the absence of oxygen at the aforementioned temperatures. During the pyrolysis process, the various compounds of the feedstock are decomposed and / or recombined, etc., thereby forming various pyrolysis oils, gases, and SIR materials. The pyrolysis reaction time may be different for each of the six reactors described in FIG. 1, but is desirably approximately the same. That is, at least 0.5 hours to about 6 hours, or any other pyrolysis time, with about 3.5 to about 4.5 hours being preferred. The reaction time also has time duration stages, e.g., stage 1 is the first hour of the reaction time, and stage 2 is the remainder of the reaction time. During these time duration stages, different compounds are obtained. For example, in time stage 1, the vapors can condense and contain preferentially chlorides and other contaminants that can be removed, thus reducing the load of contaminants in the final product from stage 2. The structure of the various pyrolysis reactors as shown in FIG. 2 is described below. As described with respect to the loading cycle, the pyrolysis reaction cycle is generally controlled so that the overall reaction period is approximately the same.

[0013] Pyrolysis vapors from the batch reactor are collected in pipes or ducts and fed to a gas separator condensing system. The condensing system can be of the direct contact type, such as a spray column, tray column, or Venturi type mixer with recirculation; or of the more typical condenser designs, such as an air cooler or shell-and-tube condenser. Cooling methods can be direct or indirect, such as using already condensed liquid or air, water, thermal oil, etc.

[0014] Also, the product gas of the pyrolysis reaction cycle as shown in FIG. 1 can be fed from each reactor I-VI through the discharge pipeline or discharge duct 18 to the gas separator 15. The pyrolyzed liquid chemical compounds and the produced SIR compounds are generally transported from the bottom of each reactor through the pipeline 20 to the chemical liquid and SIR separator 17 as shown in FIG. 1. Each pyrolysis reactor is operated sequentially with respect to the adjacent reactor. For example, when the discharge of chemical compounds and / or gas from the batch reactor I is finished, after a delay or in a sequential time manner or for a subsequent period, the reactor II also discharges gas to the separator 15 and liquid chemical compounds to the separator 17. Thus, the plastic waste 2 in the vessel 1 is pyrolyzed in the reactors I-VI in a timely and sequential manner.

[0015] The chemical liquid and SIR separator can be a flash vessel, some type of dryer, etc. to remove entrained liquid from the solid SIR material. The separator also includes a means to remove the SIR material from the system while maintaining a vapor seal. This can be via an airlock valve, piston, auger, etc.

[0016] The batch pyrolysis reactor system of the present invention is generally more efficient than a continuous reactor system. That is, the individual pyrolysis of a limited amount of plastic feedstock, such as during the loading time mentioned above, results in efficient molecular breaking, recombination, decomposition, etc., as opposed to continuous operation on a 24-hour, at least 7-days-a-week cycle. The start-stop pyrolysis of a certain amount of feedstock for a limited time obviously results in the rapid production of the various pyrolysis oils, gases, etc. mentioned above. In other words, contrary to expectations, the batch pyrolysis system of the present invention is more efficient than a continuous pyrolysis process and produces a higher amount of pyrolysis products. Furthermore, sequential batches allow the separation of undesirable contaminants such as chlorides, sulfur, ammonia, etc. by concentrating them in the time-staged products, whereas in a continuous reactor, these contaminants are evenly distributed throughout the products. Heteroatoms, such as halides, as well as other contaminants and vapors as mentioned herein, can be removed early in the total reaction run time, which may generally range from about 15 to about 60 minutes, desirably from about 20 to about 50 minutes, and preferably from about 25 to about 40 minutes.

[0017] The final treatment step of the batch reactor pyrolysis process of the present invention is the discharge of the various pyrolysis oils, gases, and SIR compounds produced. Generally, when the pyrolysis reaction occurring in the pyrolysis vessel 12 of the present invention is completed, the oil and gas remaining in the reactor are drawn off and collected. The remaining SIR materials, i.e., unfractionated compounds, which may be in the form of cracked shorter molecular chains or the like, are retained in the reactor as solid residue discharge material 5 as shown in the lower right half of FIG. 2. Materials not previously collected in the discharge reservoir (not shown) are removed by various means from the pyrolysis reactor during the discharge cycle when the temperature drops to about ambient temperature. Methods of removal include augers, conveyors, air conveyors, pistons, and the like. Since SIR is a solid material, it generally takes a long time to remove it. A suitable downtime is generally about 1 to about 6 hours, desirably about 1 to about 3 hours, and preferably about 2 hours. Once the material has been removed, the reactor is ready to be loaded as previously described herein, and the above cycle of loading, pyrolysis reaction and evacuation is repeated many times.

[0018] By operating in a sequential batch manner, different conditions can exist in the reactor during different steps, which facilitates important results. For example, during the removal of SIR, the pressure in the reactor can be lowered so that there is less leakage from the seals of the SIR removal system. This simplifies the design and makes the operation of the SIR removal system safer. However, lower process pressures may not be favored during the reaction, resulting in lower production. By performing these steps sequentially, the conditions for each can be optimized. In another example, certain reactions occur at different conditions that may be favored in sequential batch reactions. The dechlorination of PVC generally occurs at lower temperatures than the pyrolysis of the hydrocarbon chains. Thus, by operating in sequential batches, the dechlorination can be performed separately from the bulk pyrolysis, and the time sequence can reduce the chlorides in the final product. In practice, the gases can be condensed separately at the beginning and end of the run, either by using different condensers or by emptying the product vessel midway through the run, to remove halogens, especially chlorides, from the design product that is condensed later in the batch run.

[0019] The pyrolysis reaction system of the present invention of FIG. 2 on raw material or plastic waste 2 produces a variety of chemical compounds as mentioned above, including large amounts of petroleum gas such as paraffins, isoparaffins, olefins, naphthenes and aromatics.

[0020] A unique advantage of the pyrolysis batch reactor system of the present invention as shown in Figure 1 is that if any individual reactor experiences a problem, the system continues to operate as the particular individual non-functioning or failed reactor can be shut down while the remaining reactors continue to operate fully. Subsequent reactors may be operated based on the same original time or may be operated earlier.

[0021] Examples of production cycles for six different reactors are shown in FIG. 3. Not only does the time sequence of the present invention help to produce high output, but the delayed time sequence allows the human operator of the system sufficient time to handle the production cycle, e.g., loading, pyrolysis, and discharge of any residual reactants. For each reactor, a set of three downward arrows is shown that relate to the various sequential production cycles. The left arrow represents the loading time of the feedstock, the center arrow represents the time for the pyrolysis process, and the third arrow on the right side of each column represents the reactor drain and cleaning time. As is evident from FIG. 3, for each subsequent reactor, the initial loading time of the feedstock is about 2 hours. The reaction time is about 4 hours, and the drain or cleaning cycle is about 2 hours. Of course, as will be apparent to one skilled in the art, the various time cycles may vary depending on the type of reactor used, its individual characteristics, the number of reactors used, etc. Thus, there are many different types of sequential pyrolysis of waste feedstocks.

[0022] It is desirable that as many, and preferably all, of the reactors for pyrolyzing waste materials be within the ranges of characteristic and structural values ​​described herein. The characteristic values ​​generally include a low amount of oxygen in the reactor, a free volume generally greater than at least 60%, and preferably greater than 80%, and pyrolysis temperatures as described above. Structural value limitations include the shroud 7, heater H 1 , H 2 , etc., and heating fluid flow paths such as 8,9. However, it is within the scope of the present invention that one or more individual pyrolysis batch reactors can be operated outside the desired and preferred ranges described herein. That is, in general, the present invention may relate to at least two reactors, or a very small number of reactors operated within the various parameters of the present invention, such as at least 10% or more of the reactors, desirably at least 25% or more, and preferably at least 45% or more of the total individual pyrolysis batch reactors. However, to increase efficiency, it is highly desirable that at least 75% of the reactors, desirably at least about 85%, and most preferably at least 95% or more, are operated within the ranges of the property and structure values ​​set forth in the present invention.

[0023] In summary, the multiple pyrolysis batch reactors are operated independently of one another and generally have similar operating parameters, although each pyrolysis reactor may also be operated with different operating parameters such as reaction time of the plastic waste feedstock therein, type of individual waste feedstock, pyrolysis reaction temperature, discharge time, and time to load subsequent reactors. The end result of a pyrolysis batch reactor system such as that shown in Figure 1 is an intermittent but steady discharge of the aforementioned produced chemical compounds and / or gases.

[0024] In order to obtain smooth operation of the batch reactor of the present invention, it is desirable to avoid the use of the following items, compounds, etc. For example, the plastic waste feedstock vessel 1 does not include acidic compounds and other undesirable compounds such as halogens, metals, minerals, fibers, wood or food waste. The term "free" means that a small amount of undesirable compounds is used, such as less than about 10% by volume, desirably less than about 2% by volume, and preferably zero. Another operational feature of the batch reactor of the present invention is that heat is directly introduced into the reactor vessel 12 from the bottom 14 of the reactor vessel 12. Heat is also supplied into the reactor through the internal space or fluid flow passages 8 and 9 located between the reactor vessel wall 10 and the outer shroud 7. Pyrolysis batch reactors generally incorporate a helical screw, anchor mixer, or other type of agitator 4, and do not include (have) any internal perforated plates. As described later in this specification, the reactor is first purged of oxygen. The amount of oxygen in the reactor is less than about 3%, desirably less than about 2%, and preferably less than about 1.0% of the total reactor volume. The reactor is generally free of water since water or any water vapor (e.g. steam) is also removed. That is, the amount of such water is small, generally less than about 5% by volume, desirably less than about 2% by volume, and preferably less than about 1% by volume. Another negative limitation is that the plastic waste feedstock, etc., does not contain any oil, such as shale oil, that would reduce the recycled plastic content of the product. If present, it contains only small amounts, such as less than about 10% by volume, desirably less than about 3% by volume, or zero, i.e., no oil at all.

[0025] The present invention will be better understood from the following description of preferred components of a pyrolysis batch reactor that can be utilized in the present system, which generally operates on the same principles and has the same structure, characteristics and feedstocks as described below in this specification.

[0026] The feedstock is always a mixed polymer of at least two different polymers, for example a mixture of two or more of a thermoplastic polymer, a thermosetting polymer or blends thereof.

[0027] The polymeric material may include one or more of the following thermoplastic polymers, thermosetting polymers, or sustainable biopolymers, or any combination thereof: polyethylene, polypropylene, polyester, acrylonitrile-butadiene-styrene (ABS) copolymers, polyamides, polyurethanes, polyethers, polycarbonates, poly(oxides), poly(sulfides), polyarylates, polyetherketones, polyetherimides, polysulfones, polyurethanes, polyvinyl alcohols, and polymers produced by polymerization of monomers such as dienes, olefins, styrenes, acrylates, acrylonitrile, methacrylates, methacrylonitrile, diacids and diols, lactones, diacids and diamines, lactams, vinyl halides, vinyl esters, block copolymers thereof, and alloys thereof. Polymers that produce halides upon thermal decomposition, such as polyvinyl chloride, polytetrafluoroethylene, and other halogenated polymers, may be corrosive, but may be acceptable.

[0028] Polymeric materials may also include thermosetting polymers such as, for example, epoxy resins, phenolic resins, melamine resins, alkyd resins, vinyl ester resins, unsaturated polyester resins, crosslinked polyurethanes, polyisocyanurates, polyisoprene, polybutadiene, styrene-butadiene, styrene-isoprene, ethylene-propylene-diene monomer polymers, crosslinked elastomers and blends thereof, including, but not limited to, the following:

[0029] The blended polymeric materials may also include sustainable bio-based materials such as biopolymers. Biopolymers can be sustainable, carbon neutral, and renewable because they are made from plant materials that can be grown indefinitely. These plant materials are derived from non-edible agricultural crops. Examples of biopolymers include, but are not limited to, polylactic acid (PLA) and polyhydroxyalkanoates (PHAs), which are used in multi-layer sheets for food packaging applications.

[0030] The polymeric materials contained in the scrap materials can have a combination of thermoplastic and thermosetting polymers, such as tires, paints, adhesives, and automobile shredder waste (fluff), and can be used as feedstock according to the various examples of pyrolysis processes herein.

[0031] The mixed polymer feed may contain, on average, in the range of about 2% to about 25% by weight, in other examples, in the range of about 3% to about 20% by weight, in other examples, in the range of about 3% to about 15% by weight, and in yet other examples, less than about 7% by weight of fillers, contaminants, etc., based on the average weight of all solid ingredients.

[0032] In any of the above batches, the feed composition comprises from about 40% to about 90%, in another example from about 50% to about 85%, and in another example from about 70% to about 80% by weight of one or more polymers of polyethylene, polypropylene, polyester, and optionally polystyrene, with the remaining polymers including, but not limited to, polyurethane, nylon, PET, and polyvinyl chloride.

[0033] Any of the aforementioned feedstocks may be introduced into the reactor substantially as chopped polymer, and in other instances, at least a portion of the feedstock may be present in other forms, for example, the feedstock may be present in the form of molded or extruded polymer, sheet, film or multi-layer film, and foamed sheet or molded article.

[0034] The size, e.g., weight, of the plastic waste fed to any individual pyrolysis batch reactor will generally vary with reactor size and can be from about 5% to about 80% full by liquid volume, or even higher, such as from about 80% to about 95%, or lower, such as from about 0.5% to about 5%, depending on the reactor size.

[0035] This specification fully incorporates by reference U.S. Patent No. 10,711,202 as well as U.S. Patent No. 11,118,114, and it should be noted that these patents generally incorporate the batch reactor design referenced therein and therefore portions of these patents are repeated.

[0036] As mentioned above, the present invention relates to an apparatus and process for pyrolyzing plastic waste to produce various chemical compounds such as petroleum products, various gases as well as SIR (Solid Inert Residue). Plastic waste generally includes several types of polymer waste or equivalents. Various products include, but are not limited to, naphtha, distillate oil (e.g., diesel, gasoline, heating oil, natural gas, kerosene, various C1-C5 alkanes), and gas oil (e.g., heavy oil and wax). The processes herein for producing petroleum products can produce at least 50%, in other examples about 50% to about 90%, in other examples about 60% to about 90%, and in other examples about 70% to about 90% of fungible products. Exemplary embodiments of the processes herein can produce at least about 55%, in other examples about 60% to about 90%, and in other examples about 70% to about 92% of condensable gases based on the gas products produced by the process.

[0037] The process to produce petroleum products involves the pyrolysis of a feedstock containing mixed polymers and in situ reactions to produce solid inert residues, molten fluids and gases in a reaction vessel. A solid inert residue stream, a gas product stream and a small liquid stream exit the reactor. The bulk conversion of the feedstock to condensable and non-condensable gas products occurs in the reaction vessel. Up to about 100% by weight of the condensable gas products are converted to usable fuel products and up to 100% of the non-condensable gases can be used as fuel.

[0038] The term "batch process" as used herein refers to a process in which all solid, semi-molten or molten reactants (feedstocks) are placed in a reactor at the beginning of the process and then processed according to a predetermined reaction process, during which no additional feedstocks are added to the reactor. It also refers to sequential pyrolysis of additional "batch" reactors, in which gas products, liquid products and SIR are independently produced in separate or individual reactors in a time-interrupted manner. Thus, the following description relates to various operating aspects of each individual reactor of the multiple reactors that make up the batch reactor process of the present invention. Although multiple batch reactors are used separately to process a certain amount of feedstock, it should be understood that depending on the nature of the feedstock, the operating characteristics of the reactors, etc., the separate individual reactors may generally be operated in slightly different reaction regimes, such as with respect to the temperature of the individual batch reactors.

[0039] The invention involves gas cracking reactions combined with condensation and recombination reactions to achieve a desired gas product composition exiting the reactor. One or more reactors, preferably multiple separate pyrolysis batch reactors, are used to convert the plastic feedstock into various chemical compounds and / or gases. The process to produce petroleum products and / or gases involves managing the reaction chemistry within the reaction vessel.

[0040] A significant advantage of the batch process of the present invention is that instead of one long continuous 24 / 7 run where reactors may become clogged, fouled or fail, if one or more of the multiple reactors become clogged, fail or fouled, they can simply be taken out of rotation and the batch process operation continues thereby producing the desired chemical compounds and / or gases.

[0041] Thermal energy can be independently supplied and removed from the single reactor vessel. A temperature gradient exists within the reactor 11 between the bottom of the reactor vessel and the top of the reactor at the reactor outlet. The process disclosed herein has been found to produce petroleum products of desired compositional distribution from a wide variety of mixed polymers, including mixed polymer scrap. Feedstocks of inconsistent compositional mixtures can produce substantially the same target distribution of the same product composition, i.e., the desired "compositional distribution." For example, products produced by the process herein can include naphtha, distillate, wax and gas oil of the target composition, desired percentage range, respectively. The present invention exhibits controlled consistency in petroleum products. The composition of the hydrocarbon feedstock material can vary from about 10% to about 70% polyethylene, about 10% to about 70% polypropylene, about 10% to about 30% polystyrene, and about 0% to about 30% other commonly used polymeric materials, including, but not limited to, polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, nylon, and the like. In another example, the feedstock comprises at least 40% by weight mixed polymer scrap, the polymer scrap comprising at least 45% by weight to about 70% by weight, or about 80% by weight hydrocarbon-based material.

[0042] 2 is a schematic diagram of a system or apparatus 11 for accomplishing pyrolysis of mixed polymers, according to one embodiment of the present invention. The reactor vessel 12 is surrounded by a shroud 7 that forms passages 8 and 9 for carrying hot steam from heaters H1 and H2 to the periphery of the vessel 12. Baffles 25 attenuate the hot air to regulate the temperature and temperature profile inside the reactor and to affect the temperature gradient along the top to bottom of the vessel wall 10. Heaters H 1 and H 2 The burner may be of any kind, for example a gas-fired burner, acting directly on the wall of the reaction vessel 12 or including a spreader plate above the burner to distribute the heat more evenly to the bottom wall 14 of the vessel 12. Inside the reactor is an agitator 4, which may be an anchor mixer, a helical stirrer, or any other type of agitator that scrapes the bottom of the vessel and agitates the pyrolyzable plastic to maintain good heat transfer.

[0043] With continued reference to FIG. 2, the feedstock 2 is bulk-charged into the reactor through port 3. The feedstock may be fed through an auger, extruder, airlock valve, etc., and may be purged to remove air from the reactor. Additionally, the reactor is depressurized or the plastic is fed when the reactor is cold to reduce the possibility of leaks during loading of the plastic. The reactor is generally purged with an inert vapor, such as nitrogen or steam, before heating, but it is preferred that the reactor remain deaired between batches. The plastic is heated through the bottom wall 14, and the vapor is removed through the vapor port 13 in stages to separate contaminants from the final product. For example, stage A would occur early in the pyrolysis when the temperature of the plastic is low, about 200°F to about 550°F (93°C to 288°C). During stage A, the recovered vapors are rich in contaminants such as chlorides, sulfur, ammonia, and other heteroatomic contaminants. This stage A vapor can be recovered in a separate condenser or vented from product recovery before the next stage to prevent mixing of the stage A product with the final stage B product. This allows for the removal of contaminants from the final product. Stage B vapor is generated later in the pyrolysis when the plastic is at a higher temperature, e.g., between 650°F and 1350°F (343°C and 732°C), is less contaminated with the aforementioned heteroatom contaminants, and is condensed separately without mixing with the condensed product of stage A. Both products are then sent to purification and other product recovery steps. Although only two stages are assumed in this example, it is easy to see that any number of time-staged stages can be used to achieve a higher quality product, not only in terms of heteroatom contaminants in the hydrocarbon product, but also in terms of undesirable or desirable components such as paraffins, olefins, naphthenes, and aromatics. Operating the process in sequential batches allows for time stages equivalent to temperature stages, which is not possible in a purely continuous system. Batch operation further allows other characteristics of the time stages to be modified to obtain comparable product quality results.For example, pressure can be varied between stages, additives can be added in stages to adsorb contaminants, catalysts can be added between stages to effect a desired reaction, mixing speeds can be changed between stages, residence times can be changed between stages, and the overall temperature or temperature profile can be changed to achieve a desired result.

[0044] Still referring to FIG. 2, the solid inert residue remaining after the plastic is completely pyrolyzed is removed from the reactor vessel 12 through port 5 using a SIR removal system 6. This SIR removal system can be an auger, piston, continuous airlock valve, or any other solid removal system. To make the removal of the SIR safer, the SIR can be removed after the reactor cools down, reducing the pressure of the unit and minimizing the possibility of leakage from the SIR system. Additionally, the removal of the SIR can be made safe by purging the reactor with an inert vapor such as nitrogen. To minimize downtime, cool-down time, and the risk of fire or the creation of harmful combustion by-products, it is generally desirable to remove the air from the reactor between runs. For example, if the reactor is not completely cooled or there is residual SIR above the autoignition temperature, any air getting into the reactor between batches could cause the SIR to burn and produce dioxins, or convert the heavy metals in the SIR into leachable forms that become harmful.

[0045] To clarify how the invention works, the following description reflects what happens in a single reactor as it goes through its cycle. This same cycle is run in other reactors in a sequential batch system, but they are generally at different stages of the cycle at any one time. Typically, the reactor, which is still airless and still warm from the previous cycle, is charged with fresh plastic through an air-excluded feed unit such as an extruder, auger, or continuous airlock valve. The heater H is then turned on while the agitator agitates the plastic. 1 and H 2The reactor is heated directly from the bottom 14 by the heater. As the plastic heats up, first light volatile materials such as steam, low boiling organic contaminants, etc. start to erupt, initially at the top of the reactor where the steam condenses on the walls and flows back into the molten plastic by gravity, where it is volatilized again by the heater at the bottom of the reactor. Eventually, the reactor vessel warms up enough to allow the steam to leave the vessel through the steam port, where it can be condensed via the condensation system. As the reactor heats up to 212°F-575°F (100°C-302°C), the plastic material melts and the first contaminants start to be released. Chlorides, especially from PVC resin, are converted to HCl and released into the gas phase. These contaminants are collected in a condenser through the steam port. When the target amount of contaminants is released, usually measured by reaching a certain temperature set point, the contaminants are then discharged from the condenser's collection vessel. Alternatively, a separate vapor collection system for the contaminants can be used, in which case valves can be used to divert the vapors between stages of the reaction. The separate vapor collection system could be a condenser, or an adsorption bed or process to collect the contaminants and prevent them from being released into the environment. Once the contaminant removal stage is complete and the collected vapors are separated from the rest of the process, the temperature is then raised to achieve complete pyrolysis of the plastics by measuring the temperature at the bottom 14 via a measurement sensor 16. This temperature can be between 800°F and 1500°F (427°C and 816°C). During pyrolysis, the plastics are heated from the bottom 14 and a temperature difference is maintained between the bottom 14 and the top 26 of the reactor. The cooler temperature at the top of the reactor, which can be about 38°C to about 204°C lower than the bottom of the reactor, causes the vapors to condense at the top of the reactor and flow back by gravity to the heated surface of the reactor. This reflux is important because it allows the very heavy hydrocarbons to be re-broken into smaller hydrocarbons that are less likely to foul the exchangers or piping. The vapors from the pyrolysis stage are collected through a vapor port and condensed in a condenser such as a direct contact condenser, shell-and-tube condenser, or finned fan condenser. This second collected vapor is the desired product, which contains less contaminants since the contaminants were removed in the initial stage.Once pyrolysis is complete, as observed by measuring the weight of the vessel, the agitator power requirement, the steam production rate, the steam temperature, or other suitable indicators, the SIR removal process can begin. In the most preferred embodiment, the reactor is kept at approximately the same temperature and the SIR is agitated or conveyed to a SIR removal system at the bottom of the reactor. The SIR removal system can be an auger, extruder, piston, two airlock valves, or similar device that allows air to be excluded from the reactor and solids to be removed while maintaining a seal to prevent hot hydrocarbon vapors from exiting the reactor. During the SIR removal step, the reactor pressure can be reduced to reduce the possibility of steam leakage through the SIR removal system. Once the SIR is completely removed, the reactor is ready to repeat the cycle of adding plastic to the vessel.

[0046] The process is anaerobic in operation. The term "anaerobic" refers to the use of oxygen gas, O 2 , or "free" or "unbound" oxygen content, or refers to an environment having low or near zero oxygen content. That is, during the initial heating of the feedstock entering reactor 11, and throughout the pyrolysis process, reaction vessel 12 contains less than about 3% oxygen by volume, in another embodiment less than about 2% oxygen by volume, in another embodiment less than about 1% oxygen by volume, and in yet another embodiment about 0.01% to about 1% oxygen by volume, based on the internal volume of the reaction vessel.

[0047] The loading of raw materials into the reaction vessel 12 of the reactor 11 is controlled to suit the size and shape of the reaction vessel for the particular batch being loaded.

[0048] The average loading area of ​​the feedstock takes into account the variation in bed depth depending on the geometry of the reactor. In the exemplary embodiments described herein, the reactor has a depth or diameter sufficient to allow for a layer of residual solids to form during pyrolysis, and also has sufficient headspace above the feedstock to allow for controlled gas-phase decomposition and recombination reactions. The reactor has at least about 30% free volume when initially heated, in some embodiments at least about 60% free volume when heated, in other embodiments at least about 80% free volume when heated, and in other embodiments from about 60% to about 99% free volume when heated.

[0049] Products in the form of gaseous products and residual products (chemical compounds) can be recovered from the reactor. The total amount of gaseous products produced from the reactor 11 comprises at least about 50% by weight, in another example at least about 82% by weight, in another example at least about 93% by weight, and in another example at least about 96% by weight, based on the weight of the feedstock. The condensable hydrocarbons vary from about 50% by weight to about 98% by weight, and in another example from about 60% by weight to about 90% by weight, based on the total amount of gaseous products produced. For example, the condensable hydrocarbons produced include at least one of three streams, e.g., naphtha, distillate, and gas oil, at about 10% by weight to about 60% by weight, based on the weight of the gaseous products produced. For example, the condensable hydrocarbons produced may include, based on the weight of the gaseous product, from about 10% to about 60% by weight, and in another example, from about 15% to about 35% by weight, naphtha; from about 10% to about 60% by weight, and in another example, from about 15% to about 35% by weight, distillate; and from about 10% to about 60% by weight, and in another example, from about 15% to about 35% by weight, fuel oil.

[0050] Several control variables are relevant to control the rate of gas production by decomposition and reforming and the types of molecules in the gas phase, including, but not limited to, the energy input to the reactor 11 or reaction vessel 12, the heat flux, the mass flow rate of gas leaving the reaction vessel 12, the flow of gas, e.g., exhaust gas, along the outside of the reaction vessel, the thickness of the residual solid layer, the horizontal temperature gradient, the radial temperature gradient, the reaction chamber geometry, the ratio of residual solid, liquid, bubble, and gas regions, the location of product gas removal, the vertical temperature gradient, and the residence time of the gas product.

[0051] At least one temperature sensing element, e.g., a thermocouple, is disposed within the reactor 11 to provide an output signal representative of the temperature of any gaseous reaction products within the reaction vessel. The reactor 11 may include temperature sensors in the vapor space 27 via sensor 28, in the heated section of the bottom 14 of the vessel 12 via sensor 16, in the vapor outlet 13, in the SIR outlet 5, in the flow passage between the shroud and the vessel wall 10, etc. If the measured temperature is below a predetermined temperature control value, the heat source is adjusted to increase the heat input rate to the reactor. If the measured temperature in an area is above a predetermined temperature control value, for example, a heat damper is adjusted to increase the mass flow rate of plenum gas or exhaust gas through the exhaust.

[0052] To more clearly illustrate certain embodiments of the present invention and the associated advantages, examples have been described, however, there are many different embodiments within the scope of the present invention and should not be limited to the specific examples provided herein.

[0053] example It has been found that the pyrolysis batch process embodiment of the present invention produces relatively low amounts of SIR compounds as well as relatively high yields of various gaseous and liquid compounds. Exemplary processes and apparatus for the high yields of chemicals and gases obtained from the systematic batch pyrolysis of plastic waste feedstocks are now described in the following examples.

[0054] During the extended batch run, samples of the condensed hydrocarbons were taken and analyzed for chloride content using X-ray fluorescence spectroscopy. At the start of the run, the chloride content was 606 ppm. At the end of the run, the chloride content in the hydrocarbon samples was 121 ppm. This is an 80% reduction in chloride. The relative abundance of chlorides at the start of the run suggests that the chlorides can be separated by running in sequential batches, where earlier products contain preferentially chlorides and later products are relatively depleted in chlorides. Chlorides and other halogens are undesirable in the final product because they can cause corrosion in fuel and chemical feedstock applications. In a continuous process, chlorides must be removed in post-processing using expensive operations such as hydrotreating, which requires a separate process to supply hydrogen and high-pressure, high-temperature equipment with high capital costs.

[0055] In the early stages of batch pyrolysis, temperature steps can also be used to preferentially remove other heteroatoms that are undesirable as fuels or chemical feedstocks. For example, some of the nitrogen components of waste plastic feedstocks can be removed as ammonia at lower temperatures (e.g., 200°C-300°C, i.e., 392°F-572°F) than bulk pyrolysis (350°C-700°C, i.e., 662°F-1292°F), and some of the sulfur compounds can be removed as hydrogen sulfide. Ammonia and hydrogen sulfide, along with hydrochloric acid, which volatilizes at lower temperatures, can be removed from the hydrocarbon vapors by condensation as well as by typical adsorption or absorption processes to prevent them from being released into the environment or included in the final product.

[0056] During a batch run at an operating pressure of approximately 5 psig, a hydrocarbon vapor leak from the SIR removal unit was detected by the detection of carbon monoxide on the gas detector. Reducing the pressure in the system to 1 psig eliminated the leak as no carbon monoxide readings were found on the monitor.

[0057] While in accordance with the patent statutes, the best mode and preferred embodiment has been set forth, the scope of the invention is not limited thereto, but rather by the appended claims.

Claims

1. 1. A method for producing and recovering chemical compounds and / or gas products from a plastic waste feedstock, comprising: providing a plurality of separate pyrolysis batch reactors, each capable of independently converting said plastic waste feedstock into chemical compounds and / or gas products, and also into a solid inert residue (SIR); independently charging the plastic waste feedstock into at least a first pyrolysis batch reactor and a second pyrolysis batch reactor in a sequential time manner; independently pyrolyzing the plastic waste feedstock in the first pyrolysis batch reactor and the second pyrolysis batch reactor in a time-sequential manner; and producing and discharging said chemical compounds and / or gas products as well as said solid inert residue (SIR) from said at least first pyrolysis batch reactor and said second pyrolysis batch reactor in an independent time sequential manner. The method includes:

2. 10. The method of claim 1, wherein at least the first pyrolysis batch reactor has a free volume of at least 60% based on the amount of the polymeric feedstock in the reactor, and the pyrolysis temperature of the at least first separate pyrolysis batch reactor is from about 500°F (260°C) to about 1500°F (815°C).

3. 3. The method of claim 2, wherein at least the first pyrolysis batch reactor has an oxygen content therein of less than about 3% by volume.

4. 4. The method of claim 3, wherein the at least one individual pyrolysis batch reactor has an oxygen content therein of less than about 2% by volume.

5. loading at least about 85% of said plurality of individual pyrolysis batch reactors with said plastic waste feedstock; independently and sequentially pyrolyzing the plastic waste feedstock in the plurality of separate pyrolysis batch reactors; and producing said chemical compounds and / or gas products from said plurality of separate pyrolysis batch reactors; 3. The method of claim 2 comprising:

6. 6. The method of claim 5, wherein each of the plurality of individual pyrolysis batch reactors independently has a plurality of heaters therein capable of forming a heated gas exchange medium.

7. 7. The method of claim 6, further comprising an outer shroud substantially surrounding each of the plurality of individual pyrolysis batch reactors, each of the plurality of shrouds comprising the pyrolysis batch reactors independently comprising a plurality of sequential reaction zones, and wherein the plurality of pyrolysis batch reactors independently have at least about 80% by volume of free volume.

8. the plurality of individual pyrolysis batch reactors each having a plurality of independent interior walls extending between the reactor and the outer shroud and independently defining a plurality of fluid flow paths along a horizontal length of the reactor; The method of claim 7 , wherein the fluid flow path is capable of containing the heated gaseous medium therein.

9. 4. The method of claim 3, wherein the plastic waste feedstock comprises one or more of thermoset polymers including polyethylene, polypropylene, polyester, acrylonitrile-butadiene-styrene (ABS) copolymers, polyamides, polyurethanes, polyethers, polycarbonates, poly(oxides), poly(sulfides), polyarylates, polyetherketones, polyetherimides, polysulfones, polyurethanes, polyvinyl alcohols, and polymers produced by polymerization of monomers such as dienes, olefins, styrenes, acrylates, acrylonitrile, methacrylates, methacrylonitrile, polymers of diacids and diols, lactones, polymers of diacids and diamines, lactams, vinyl halides, vinyl esters, block copolymers thereof, and alloys thereof; and thermoset polymers including epoxy resins, phenolic resins, melamine resins, alkyd resins, vinyl ester resins, unsaturated polyester resins, crosslinked polyurethanes, polyisocyanurates, and crosslinked elastomers including polyisoprene, polybutadiene, styrene-butadiene, styrene-isoprene, ethylene-propylene-diene monomer polymers; and any combination thereof.

10. 4. The method of claim 3, wherein the plastic waste feedstock comprises polyethylene, polypropylene, polyester, polystyrene, polyurethane, polyamide, polymethyl methacrylate, polyvinyl chloride, or any combination thereof.

11. 6. The method of claim 5, wherein the plastic waste feedstock comprises polyethylene, polypropylene, polyester, polystyrene, polyurethane, polyamide, polymethyl methacrylate, polyvinyl chloride, or any combination thereof.

12. 4. The method of claim 3, wherein the produced chemical compounds include heating oil, gasoline, diesel fuel, kerosene, natural gas, wax, lubricating oil, naphtha, distillate, or any combination thereof.

13. 7. The method of claim 6, wherein the produced chemical compounds include heating oil, gasoline, diesel fuel, kerosene, natural gas, wax, lubricating oil, naphtha, distillate, or any combination thereof.

14. independently loading said plastic waste feedstock into each of said plurality of said individual pyrolysis batch reactors; independently pyrolyzing each of said plastic waste feedstocks in said plurality of separate pyrolysis batch reactors in a sequential time-based manner; producing said chemical compounds or gas products, or both, from each of said plurality of separate pyrolysis batch reactors; 8. The method of claim 7, comprising:

15. 10. The method of claim 1, wherein a portion of the produced product in the first reactor or any subsequent reactor is removed early in the batch run of the reactor to reduce the heteroatom content in the reaction product.

16. 10. The method of claim 1 further comprising the step of removing at least one gas product from said reactor prior to removing said solid inert residue.

17. A plurality of pyrolysis batch reactors, the reactors comprising a shroud substantially surrounding each of the batch reactors; each of the reactors independently comprises one or more interior walls extending between the outer shroud and the pyrolysis reactor and defining a plurality of fluid flow passages along a horizontal length of the reactor vessel, the fluid flow passages capable of containing a heated gas exchange medium therein; Each of the plurality of reactors independently comprises at least 60% free volume; and The plurality of batch reactors are capable of sequentially decomposing and reforming the plastic feedstock and independently producing chemical compounds or gas products, or both, in a sequential time-based manner. Multiple pyrolysis batch reactors.

18. 20. The multiple pyrolysis batch reactor of claim 17, comprising a plurality of heaters, said heaters capable of independently heating said fluid flow paths with a gas medium.

19. 20. The plurality of pyrolysis batch reactors of claim 18, wherein each of the separate pyrolysis batch reactors independently comprises one or more reaction zones therein.

20. 20. The plurality of pyrolysis batch reactors of claim 19, wherein each of the pyrolysis batch reactors includes a mixer for advancing the feedstock through the reactor.

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